package net.neoremind.mycode.argorithm.leetcode;

import net.neoremind.mycode.argorithm.leetcode.support.TreeNode;

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;

/**
 * Given a non-empty binary tree, return the average value of the nodes on each level in the form of an array.
 * <p>
 * Example 1:
 * Input:
 * 3
 * / \
 * 9  20
 * /  \
 * 15   7
 * Output: [3, 14.5, 11]
 * Explanation:
 * The average value of nodes on level 0 is 3,  on level 1 is 14.5, and on level 2 is 11. Hence return [3, 14.5, 11].
 * Note:
 * The range of node's value is in the range of 32-bit signed integer.
 *
 * @author xu.zhang
 */
public class AverageOfLevelsInBinaryTree {
    public List<Double> averageOfLevels(TreeNode root) {
        List<Double> ret = new ArrayList<>();
        if (root == null) {
            return ret;
        }
        Queue<TreeNode> q = new LinkedList<>();
        q.add(root);
        while (!q.isEmpty()) {
            long sum = 0L;
            int size = q.size();
            for (int i = 0; i < size; i++) {
                TreeNode node = q.poll();
                sum += node.val;
                if (node.left != null) {
                    q.add(node.left);
                }
                if (node.right != null) {
                    q.add(node.right);
                }
            }
            double res = sum * 1.0 / size;
            ret.add(res);
        }
        return ret;
    }

}
